A sudden bump on the head may be caused by trauma, or folliculitis, sebaceous cysts and other causes, it is recommended to consult a doctor in a timely manner. 1. Trauma: head bump or impact and other traumatic injuries, will lead to the accumulation of blood in the head hematoma, manifested as a hard bump, touch pain. 2. Folliculitis: Folliculitis is mainly caused by bacteria, fungi and other pathogens that cause hair follicle infections, often manifested as the formation of red papules around the hair follicle, accompanied by redness, swelling, fever, itching and other symptoms of inflammation, which occurs in the head can be manifested as a hard bump on the head. 3. Sebaceous cysts: Sebaceous cysts are mainly due to the sebaceous gland discharge duct obstruction, sebaceous gland secretions can not be discharged and the accumulation of cysts formed in the gland, often occurring in the head and face and other sebaceous secretion of the place, the main manifestation of the hard round cysts, there can be a dull pain. Suddenly raised a hard lump on the head may also be caused by other reasons, it is recommended that the patient timely to the hospital, the doctor to clarify the cause of the targeted treatment.